1. Field of the Invention
The present invention relates to an abrasive-recovery mechanism in a blasting machine and, more particularly, to an abrasive-recovery mechanism for recovering an abrasive ejected mainly in a blasting chamber formed in a cabinet of a blasting machine.
The blasting machine according to the present invention encompasses various types of blasting machines such as a sand-blasting machine for dry-ejecting or dry-projecting (hereinafter, referred to as “ejecting”, including projecting) a mixed fluid composed of a compressed gas, such as compressed air, and an abrasive; and a suction blasting machine or a direct-pressure blasting machine for use in a shot peening machine. The blasting machine according to the present invention also includes those machines for ejecting an abrasive by centrifugal force and those for ejecting an abrasive by bombarding with the use oft for example, a rotating impeller.
The abrasive to be recovered by the recovery mechanism according to the present invention includes not only the abrasive used for polishing or cutting, such as abrasive grains, but also so-called “shot” (e.g., steel balls, glass beads, plastic beads, and ceramic beads) ejected in order to endow objects to be processed or products to be treated (hereinafter, referred to as “workpieces” comprehensively) with residual stress or for the purpose of surface treatment such as coating, and further includes powders or particles to be ejected for various other purposes. In addition, the abrasive to be recovered by the recovery mechanism according to the present invention includes dust, such as powders of workpieces by bombarding and a crushed abrasive particle, generated by ejecting the abrasive, as well as a reusable abrasive.
It should be noted, however, that the following descriptions of embodiments focus on the process of recovering the abrasive. The above-described dust is transported via the same recovery route as the abrasive until it is separated from the abrasive in a dust collector.
When classified according to raw material, the above-described abrasive is made of ceramic, glass, metal, resin, or plant matter. A ceramic-based abrasive includes alundum, carborundum, garnet, zircon beads, zircon shot, zircon grit, and so forth. A glass-based abrasive includes glass beads. A metal-based abrasive includes steel shot, steel grit, steel beads, round-cut wires, stainless-steel shot, stainless-steel beads, stainless-steel cut wires, and so forth, when classified according to material and shape. A resin-based abrasive includes nylon, polycarbonate, Polyplus™, and so forth, when classified according to material. A plant-based abrasive include walnuts (walnut shells), apricots (apricot seeds), peaches (peach seeds), and so forth. As far as shape is concerned, the abrasive may be polygonal, grid-shaped, spherical, bead-shaped, cylindrical, shaped like cut wire, and so forth.
The above-described abrasive is used for the purposes of superficial delamination such as mold cleaning, coating delamination, nitriding; cleaning such as derusting and dirt removal; surface treatment such as carving, patterning, and plating; shot peening for satin-like finishing or metal finishing; and deburring of machined products, resin-molded products, or diecast products.
As far as grain size is concerned, the above-described abrasive is available in a wide variety of specifications including #30 to #280 (0.3 mm to 2.8 mm in diameter) for the metal-based abrasive with large diameters; and #20 to #220 (1000 to 53 μm), fine particle, and #240 to #8000 (57 to 1.2 μm) for the ceramic-based abrasive.
2. Description of the Related Art
As described above, the abrasive is ejected onto a workpiece to cut or clean the workpiece by sand-blasting, or shot, such as steel balls, is made to bombard on a workpiece to coat the workpiece with tin, zinc, and other metals or to endow the workpiece surface with residual stress by shot peening processing.
During the process of ejecting powders or particles onto a workpiece in this manner, the working environment is contaminated by any dispersion of the reusable abrasive that has been recovered after being ejected, the crushed abrasive particle as a result of the abrasive bombarding on the workpiece, or dust such as a cut particle of the workpiece. In order to reuse the abrasive that has been used once, it is necessary to recover the abrasive. For this reason, a blasting machine includes a cabinet in the form of a box where the abrasive is ejected and processed, and the abrasive is ejected on a workpiece in a blasting chamber formed in this cabinet to prevent the abrasive or dust from dispersing outside the cabinet.
Referring to FIG. 10, a hopper 10′ forms a lower part of a cabinet 3 and is shaped like an inverted pyramid tapering downward so that the abrasive, dust, and so forth in a blasting chamber 2 can be recovered. The bottom end of this hopper 10′ is made to communicate with a dust collector 60 through, for example, a cyclone 50, which is an abrasive tank. When a blower 61 provided for the above-described dust collector 60 sucks the interior atmosphere of the dust collector 60, the abrasive and dust recovered by the hopper 10′ are transported outside the cabinet 3. The reusable abrasive can be separated from other dust and recovered (refer to FIG. 2 of Japanese Unexamined Patent Publication No. 2005-74563).
An opening at the top of the above-described hopper 10′ is covered with, for example, a perforated metal mesh 22 that allows the abrasive to pass therethrough. This mesh 22 prevents, for example, a foreign matter from falling into the hopper 10′. At the same time, a metal grid 21 on which a workpiece W″ is disposed is provided over this metal mesh, as required, thus separating the hopper 10′ from the blasting chamber 2. The metal grid 21 and the metal mesh 22 define a bottom wall surface 20 of the blasting chamber 2.
In a blasting machine 1 constructed as described above where the hopper 10′ shaped like an inverted quadrangular pyramid, is provided at the bottom of the cabinet 3, the abrasive ejected in the blasting chamber 2, dust generated by ejecting this abrasive, and so forth fall into the hopper 10′ through the metal grid 21, the metal mesh 22, and so forth constituting the bottom wall surface 20 of the blasting chamber 2. Thereafter, the abrasive that has fallen into the hopper 10′ is guided to a sloping inner wall of the hopper 10′ and accumulates at the bottom of the hopper 10′. The accumulated abrasive is then introduced into a recovery pipe 30 that sucks the interior atmosphere of the blasting chamber 2 through the bottom of this hopper 10′ and is transported outside the cabinet 3.
The abrasive transported as described above is introduced into the cyclone 50, also serving as an abrasive tank, to recover the reusable abrasive. The dust in the form of a residue after the abrasive has been recovered is introduced into the dust collector 60, where dust-free clean air is ejected outside through the blower 61. With the above-described structure, a recovery mechanism for recovering the abrasive and dust is provided.
As shown in FIG. 10, however, if the cabinet 3 is made larger, the hopper 10′ also becomes larger because the hopper 10′ is formed by tapering the lower part of the cabinet 3 towards the bottom thereof. As a result, the bottom wall surface 20 of the blasting chamber 2 formed by covering the opening at the top of this hopper 10′ with the metal mesh 22, the metal grid 21, and so forth will be disposed at a higher position.
Thus, the structure shown in FIG. 10 has no problem in operation as long as the blasting machine 1 is small. However, if a blasting machine has the above-described structure and needs to process a large workpiece W, there is no choice but to make the blasting machine itself larger, thus also making the hopper 10′ larger. Therefore, the distance from the bottom wall surface 20 of the blasting chamber 2 to the floor surface of a building where the blasting machine is installed becomes large. This makes it difficult to transport the workpiece W up into and down from the blasting chamber 2.
In particular, when a large workpiece W needs to be handled, it would be convenient if a large space can be secured in the blasting chamber 2, i.e., a space large enough for an operator to transport the workpiece W on a cart into the blasting chamber 2 and to handle the workpiece W in the blasting chamber 2. To do this, the hopper 10 needs to be made much larger. However, allowing a cart and an operator to smoothly enter the blasting chamber 2 involves a contradicting demand; that is, the position, i.e., height of the bottom wall surface 20 of the blasting chamber 2 from the above-described floor surface needs to be lower.
Such a demand could be satisfied even with the known structure of the blasting machine 1. More specifically, a groove or a dented portion large enough to accommodate the hopper 10′ could be formed below the floor or in the base of a building where the blasting machine 1 is installed so that the hopper 10′ can be housed in this groove, thereby causing the bottom wall surface 20 of the blasting chamber 2 to be substantially flush with the floor of the building.
This approach, however, is not only money- and labor-consuming in installing the blasting machine 1 but also requires extensive renovation of the floor, the base, and so forth of the existing building. In short, this approach is difficult to adopt for existing buildings.
Moreover, if the blasting chamber 2 becomes larger as the cabinet 3 becomes large, the recovery pipe for sucking the air in this blasting chamber, the duct, the cyclone, the dust collector, the blower, and so forth also need to be made large. This makes the overall machine large and increases the cost of the machine.
The present invention has been conceived in order to overcome the above-described problems associated with the conventional art. Thus, it is an object of the present invention to provide an abrasive-recovery mechanism in a blasting machine that allows the bottom wall surface of the blasting chamber to be disposed at a lowest possible position from the above-described floor without requiring extensive renovation of the floor, the base, and so forth of the building, while still employing a structure where a hopper for recovering the abrasive is disposed below the bottom wall surface of the blasting chamber.
It is another object of the present invention to provide an abrasive-recovery mechanism in a blasting machine that, even though the blasting chamber is made larger, can recover the abrasive and similar dust without increasing the sizes of the recovery pipe that sucks the interior atmosphere of the blasting chamber, the duct, the cyclone, the dust collector, the blower, and so forth or causing any problem such as clogging.